Centrifugal slurry pumps generally include a pump casing having a pumping chamber therein which may be of a volute configuration with an impeller mounted for rotation within the pumping chamber. A drive shaft is operatively connected to the pump impeller for causing rotation thereof, the drive shaft entering the pump casing from one side. The pump further includes a pump inlet which is typically coaxial with respect to the drive shaft and located on the opposite side of the pump casing to the drive shaft. There is also a discharge outlet typically located at a periphery of the pump casing. The pump casing may be in the form of a liner which includes a main liner, and front and back side liners, which are encased within an outer pump housing.
The impeller typically includes a hub to which the drive shaft is operatively connected, and at least one shroud. Pumping vanes are provided on one side of the shroud with discharge passageways between adjacent pumping vanes. The impeller may be of the closed type where two shrouds are provided with the pumping vanes being disposed therebetween. The shrouds are often referred to as the front shroud adjacent the pump inlet and the back shroud. The impeller may however be of the “open” face type which comprises one shroud only.
One of the major wear areas in the slurry pump is the front side-liner that is adjacent to the rotating impeller. Slurry enters the impeller in the centre or eye and is then flung out to the periphery of the impeller and into the pump casing. Because there is a pressure difference between the casing and the eye, there is a tendency for the slurry to flow back to the eye through the gap between the side-liner and the impeller, resulting in high wear on the side-liner.
In order to reduce the driving pressure on the slurry in the gap, as well as create a centrifugal field to expel particles, it is common for slurry pumps to have auxiliary or expelling vanes on the front shroud of the impeller. Auxiliary or expelling vanes may also be provided on the back shroud. The expelling vanes rotate the slurry in the gap creating a centrifugal field and thus reducing the driving pressure for the returning flow, reducing the flow velocity and thus the wear on the side-liner.
A major issue for slurry pumps is the wear of the side-liner. In many applications the side-liner is the weakest point in the pump, wearing out before any other part. Much of the wear on the side-liner is a result of the flow generated by the rotating expelling vanes. In particular there is wear from the tip or outer edge of the expelling vanes due to the creation of fluid vortices and entrained particles.